Three-time world champion Mark Williams became the sixth seeded player to be eliminated in the 2024 event as he lost 10-9 in a deciding frame against China’s Si Jiahui.
Welshman Williams, the 49-year-old fifth seed, led 5-4 in his first-round match against Si after Monday’s first session.
However, last year’s semi-finalist won four frames in a row to move 8-5 ahead, before Williams pulled two frames back.
Si took the next to go 9-7 in front and had a glorious chance to seal the victory before missing a pink when 39-14 ahead to give Williams hope.
The 2000, 2003 and 2018 champion took it to 9-9, but left a red on into the middle and Si made a match-winning break of 77.
It has been a tournament of shocks and Williams joins top seed Luca Brecel, fifth seed Mark Selby, ninth seed Ali Carter, 10th seed Gary Wilson and 11th seed Zhang Anda in making an early exit.
Si will face another Welsh player in the last 16 when he meets world number 44 Jak Jones, after he defeated China’s Zhang on Sunday.
Robert Milkins, the 16th seed, almost became another seed to lose, but recovered from 24-0 down in the deciding frame to scrape through 10-9 against China’s Pang Junxu in a match that finished at 23:05 BST.
Milkins had lost the first three frames of the match and was also 9-8 behind but held his nerve to win the last two to set up a meeting with David Gilbert, who beat 2023 champion Luca Brecel on Saturday.
“I can’t believe I got through,” said Milkins. “I just didn’t play great and I was lucky that Pang didn’t play well. I had actually played OK, but even when I was 6-5 up I got down on myself.
“I’m like a dodgy horse, he hits the front and doesn’t want to get on with it. The last two frames I played OK and when I went 9-8 behind that was the only time I relaxed.”
